Inclusions and the like in molten metal containing aluminum, an aluminum alloy, and so on cause problems in casting, such as casting defects, and cracking of the resulting casting in rolling. Therefore, filtration of molten metal has been practiced to remove inclusions and the like. A filtration apparatus having one or more porous ceramic filtration tubes placed horizontally in a molten metal chamber is widely known. In a filtration apparatus of this type molten metal is made to flow from the outside to the inside of the tube to be deprived of inclusions, etc. and gain improved quality. Castings obtained from, for example, molten aluminum thus filtered have reduced cracking or scratches on rolling. Examples of such a filtration apparatus are described in Patent Literatures 1 and 2 below.
FIG. 24 schematically illustrates the structure of such a conventional filtration apparatus 210. The filtration apparatus 210 includes a housing 220 and a filtration unit 240. The filtration unit 240 includes a filtration tube 241 having its both ends supported by a pair of support plates 242 (called closure heads). The filtration unit 240 is pressed to the inner wall of the housing 220 by a wedge 290 thereby to secure a seal for molten metal. The pair of support plates 242 are supported by respective bases 230.
The assignee common to this patent application previously proposed a filtration apparatus having filtration tubes disposed in a molten metal chamber not horizontally but vertically (see Patent Literature 3 below). The embodiment shown in FIGS. 1 to 3 in Patent Literature 3 is configured in such a manner that, when the filtration unit is fitted into the housing, the longitudinal direction of the filtration tubes intersects the horizontal direction of the housing and their open end face upward.